US5350913A - Light pulse intensity regenerator, light tranforming repeater, pre-amplifier for light signal, light intensity change measuring apparatus, and stabilized light source - Google Patents

Light pulse intensity regenerator, light tranforming repeater, pre-amplifier for light signal, light intensity change measuring apparatus, and stabilized light source Download PDF

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Publication number
US5350913A
US5350913A US08/051,688 US5168893A US5350913A US 5350913 A US5350913 A US 5350913A US 5168893 A US5168893 A US 5168893A US 5350913 A US5350913 A US 5350913A
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Prior art keywords
light
electric signal
pulse intensity
regenerating apparatus
intensity
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US08/051,688
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Shinichiro Aoshima
Isuke Hirano
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Hamamatsu Photonics KK
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Hamamatsu Photonics KK
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Assigned to HAMAMATSU PHOTONICS K.K. reassignment HAMAMATSU PHOTONICS K.K. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: AOSHIMA, SHINICHIRO, HIRANO, ISUKE
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/299—Signal waveform processing, e.g. reshaping or retiming

Definitions

  • the present invention relates to a light pulse intensity regenerating apparatus enabling wave shaping.
  • FIG. 1 is a drawing to show a construction of a conventional electro-optical streak camera in which a light control device for effecting light deflection is built (as disclosed in Japanese Laid-open (Kokai) Patent Application No. 1-287425).
  • Signal light input into the device is split by a half mirror.
  • Signal light traveling straight through the half mirror is amplified by a traveling wave amplifier (as will be referred to as TWA) then to enter a light deflector.
  • TWA traveling wave amplifier
  • the other signal light reflected by the half mirror is converted into an electric signal by a photoelectric tube, and the electric signal is used as a trigger signal for light deflector.
  • Light output from the light deflector travels at an output angle according to sweep of the light deflector.
  • the light is subjected to selected filtering through a slit, and the light through the slit is then detected by a detector.
  • the conventional light controlling apparatuses do not serve as a wave shaping device. Specifically, the other light thus separated is merely used as a trigger, but is not used to effect deflection in accordance with a waveform of the separated light.
  • a light pulse intensity regenerating apparatus comprises (a) separating means for separating incident light into control light and shaping object light, (b) light detecting means for receiving the control light from the separating means to convert it into an electric signal having a value corresponding to a light amount of the received light, (c) a light amplifying section for amplifying an intensity of the shaping object light in accordance with an intensity of the electric signal output from the light detecting means, (d) a light deflecting section for deflecting the shaping object light having passed through the light amplifying section in accordance with the intensity of the electric signal output from the photo detecting means, and (e) light limiting means for permitting only light having a deflection angle within a predetermined range out of output light from the light deflecting section to pass therethrough.
  • the signal light input into the apparatus is first separated into the control light and the shaping object light by a light separator, which is a main component of the separating means, such that a ratio of intensity amplitude is constant at a time between the control light and the shaping object light.
  • the light separator comprises a half mirror or a fiber coupler.
  • the shaping object light is wave-shaped through amplification, deflection, and passing limitation at subsequent steps.
  • the control light is used for controls of amplification and deflection effected on the shaping object light at the subsequent steps in the light amplifying section and in the light deflecting section while reflecting the waveform of light input into either the light amplifying section or the light deflecting section.
  • the control light separated by the separating means is input into the light detecting means.
  • a photo detector which is a main component of the light detecting means, outputs an electric signal reflecting (for example, proportional to) a light amount received.
  • the photo detector comprises a photoelectric tube, a pin photodiode, or an avalanche photodiode.
  • the electric signal output from the photo detector is input into the light amplifying section and into the light deflecting section to control an amplification factor and a deflection angle, respectively.
  • An input timing of the electric signal into either of the light amplifying section and the light deflecting section is synchronized with a timing at which the shaping object light or the amplified shaping object light is passing through the light amplifying section or through the light deflecting section.
  • Adjustment of the synchronization is effected by adjusting an optical path of optical fiber for shaping object light or for amplified shaping object light, or by adjusting a transfer delay time of electric signal.
  • the electric signal output from the photo detector may be a current signal or a voltage signal, which may be selectively used in a suitable relation with control signal input circuits of the light amplifying section and the light deflecting section.
  • the photo detector outputs an electric signal of small value
  • the electric signal is guided through an electric amplifier then into the light amplifying section and into the light deflecting section.
  • the shaping object light separated by the separating means is input into the light amplifying section.
  • a light amplifier which is a main component of the light amplifying section, receives the electric signal output from the light detecting means and amplifies the shaping object light at an amplification factor in accordance with (for example in proportion to) a value of the electric signal.
  • the input timing of the shaping object light is synchronized with the input timing of the control electric signal. For example, if the amplification factor is proportional to the value of control electric signal and if the value of control electric signal is proportional to the intensity of control light, the intensity of the amplified shaping object light would be proportional to a square of that of the shaping object light, which makes a rise and a fall in amplified shaping object light steeper.
  • a final intensity of amplified shaping object light would be proportional to the (n+1)-th power of that of shaping object light, further making a rise and a fall in amplified light steeper and steeper.
  • a light amplifier having an amplification factor with saturation characteristics is effective for rectangular pulse formation.
  • the light amplifier may be a semiconductor light amplifier (for example see T. Saito et al., Journal of Lightwave Technology, Vol. 6 No. 11, November 1988, p1656-1664) or a fiber amplifier.
  • the thus amplified shaping object light is input into the light deflecting section.
  • a light deflector which is a main component of the light deflecting section, receives the electric signal output from the light detecting means and provides the amplified shaping object light with a deflection angle in accordance with (for example in proportion to) a value of the electric signal.
  • the input timing of amplified shaping object light is synchronized with the input timing of control electric signal.
  • a final deflection angle of amplified shaping object light would additionally increase as to be n times as large as that in case of a set of light deflector arranged.
  • a light deflector having a deflection factor with saturation characteristics is effective for rectangular pulse formation.
  • the light deflector may be for example a semiconductor light amplifier (see K. Tone et al., Appl. Phys. Lett. 56 (14), Apr. 2, 1990, p1229-1301).
  • the light output from the light deflecting section is input into the light limiting means.
  • a light limiter which is a main component of the light limiting means, comprises a slit or an optical fiber, which permits only light having a deflection angle within a predetermined range out of the output light from the light deflecting section to pass therethrough.
  • the output light from the light limiting means includes only light obtained by amplifying the shaping object light into an intensity in a predetermined range and deflecting the amplified shaping object light into a deflection angle within the predetermined range, whereby the output light may include what is obtained by amplifying only light with desired intensity out of the input signal light. If the above light deflector has saturation characteristics, light having a waveform of rectangular pulse may be obtained. Also, a direct current component may be readily removed.
  • the amplification and the deflection of light are carried out in the light amplifying section and in the light deflecting section in accordance with the intensity of light itself, and the light limiting means permits only light having a deflection angle within a predetermined range to pass therethrough, whereby the output light may be obtained in such a waveform that signal components exceeding a certain threshold value are amplified with steeper rise and fall.
  • the S/N ratio may be improved and information may be transmitted at a high reliability.
  • the intensity change of light may be measured while emphasized. Further, if a light source is controlled by feedback of the thus emphasized light intensity change thereinto, the light source may be stabilized to emit light with stable intensity.
  • FIG. 1 is a drawing to show a conventional example of light control device
  • FIG. 2 is a drawing to show an embodiment of a light pulse intensity regenerator
  • FIG. 3 is a drawing to show a construction of a light amplifying and deflecting section
  • FIG. 4 is a drawing to show a construction of a light deflecting element
  • FIG. 5 is a drawing to show a test system for evaluating characteristics of a semiconductor light amplifier
  • FIG. 6 is a drawing to show characteristics of the semiconductor light amplifier
  • FIG. 7 is a drawing to show a test system for evaluating characteristics of a semiconductor light deflector
  • FIG. 8 is a drawing to show characteristics of the semiconductor light deflector
  • FIG. 9 and FIG. 10 are drawings to show a test system for evaluating characteristics of a light deflecting element
  • FIG. 11 is a drawing to show characteristics of the light deflecting element
  • FIG. 12 is a drawing to show a test system for evaluating characteristics of a combination of semiconductor light amplifier with light deflecting element
  • FIG. 13 is a drawing to show characteristics of the apparatus as shown in FIG. 12;
  • FIG. 14 is a drawing to show a specific apparatus as an embodiment of the apparatus of FIG. 13;
  • FIG. 15 and FIG. 16 are drawings to show operations of the apparatus of FIG. 14;
  • FIG. 17 is a drawing to show applications of the light pulse intensity regenerating apparatus according to the present invention as a light transforming repeater and as a light signal pre-amplifier;
  • FIG. 18 is a drawing to show an embodiment of a light intensity change measuring apparatus.
  • FIG. 19 is a drawing to show an embodiment of a stabilized light source.
  • FIG. 2 is a drawing to show a construction of a light intensity nonlinear filter in a first embodiment.
  • Input light incident into an end of fiber is separated by a beam splitter 2.
  • Light traveling straight through the beam splitter 2 enters a light amplifying and deflecting section 4 through an optical fiber, in which the light is amplified and deflected, and through which a light component of predetermined deflection angle is extracted to be output from an optical fiber as output light.
  • the other part of light separated by the beam splitter 2 is received by a photo detector 6.
  • the light received by the photo detector 6 is converted into an electric signal therein, and the electric signal is amplified by an amplifier 8 then to be output to the light amplifying and deflecting section 4.
  • desired wave shaping may be effected by adjusting a light amplification factor, a change speed of deflection angle, and/or a range of deflection angle selected, in the light amplifying and deflecting section 4.
  • FIG. 3 shows a construction of the light amplifying and deflecting section 4.
  • the light amplifying and deflecting section 4 comprises a light amplifying element 4a and a light deflecting element 4b.
  • a semiconductor light amplifier is used as the light amplifying element 4a, and a semiconductor light deflector as the light deflecting element 4b.
  • the light amplifying element 4a and the light deflecting element 4b are so arranged that a light signal from the beam splitter 2 is synchronized in either of the elements with an electric signal from the photo detector 6.
  • an optical fiber may be present or absent in connecting portion between the elements, or, the elements may be directly connected with each other, because they are both semiconductor elements.
  • the light amplifying and deflecting section 4 can be structured as an element which can simultaneously perform the light amplification and the light deflection with a single electric signal from the photo detector 6. Such a modification obviates separate application of electric signal in the arrangement of FIG. 3.
  • a rare earth doped amplifier may also be used as the light amplifying element 4a.
  • a galvanomirror as well as the semiconductor light deflector may also be used as the light deflecting element 4b.
  • the light amplifying element 4a and the light deflecting element 4b are exchangeable in position.
  • the elements 4a, 4b may be arranged to operate in accordance with at least one of electric current amount and voltage strength of the electric signal output from the photo detector 6. It would be preferable in respect of simplification of amplification of electric signal and distribution of signal that the elements 4a, 4b both be operated with a single signal (for example a current).
  • FIG. 4 shows a construction of the light deflecting element 4b.
  • the light deflecting element 4b comprises a light deflector 14b, for example a semiconductor light deflector, and a light limiting member 24b.
  • the light limiting member 24b may be a member with an equivalent aperture of fiber end or a member using a normal slit.
  • the light input into the light deflector 14b is output therefrom at a certain deflection angle in accordance with the electric signal output from the photo detector 6. Since the light limiting member 24b is present in this arrangement, output light may include components with angle near a deflection angle ⁇ .
  • FIG. 5 shows a test system for evaluating characteristics of the semiconductor light amplifier constituting the light amplifying element 4a. Such evaluation of characteristics is carried out to determine wave shaping characteristics of the light intensity nonlinear filter of the embodiment.
  • FIG. 6 shows characteristics of the semiconductor light amplifier obtained using the apparatus of FIG. 5.
  • I in satisfies the condition of I 0 ⁇ I in ⁇ I 2 , then I out ⁇ k(I in -I 0 ) 2 where k is a proportional constant.
  • I 0 ⁇ I in ⁇ I 1 then I in ⁇ I out , which means that no light amplification is carried out.
  • I 1 ⁇ I in ⁇ I 2 then I out ⁇ I in , which means that the light amplification is carried out.
  • FIG. 7 shows a test system for evaluating characteristics of the semiconductor light deflector constituting the light deflecting element 4b. Such evaluation of characteristics is carried out to determine the wave shaping characteristics of the light pulse intensity regenerator of the embodiment.
  • FIG. 8 shows characteristics of the semiconductor light deflector obtained using the apparatus of FIG. 7.
  • FIG. 9 and FIG. 10 show a test system for evaluating characteristics of the light deflecting element which is a combination of the semiconductor light deflector of FIG. 7 with an aperture. Such evaluation of characteristics is carried out to determine the wave shaping characteristics of the light intensity nonlinear filter of the embodiment.
  • the output light from the semiconductor light deflector has a distribution ⁇ of spatial intensity as shown in FIG. 9 and FIG. 10, and if the aperture is located with center at angle ⁇ 2 behind the semiconductor light deflector, the output light with output angle ⁇ 2 may be most efficiently transmitted through the aperture. Further, if the input-output characteristics are determined such that the output light starts passing through the aperture when the distribution tail of the distribution ⁇ reaches angle ⁇ 1 as shown in Fig. 10, the output characteristics a of the light deflecting element would be as shown in FIG. 11.
  • the output characteristics a of the light deflecting element would show a difference in curvature of one point from another in I 1 ' ⁇ I in ⁇ I 2 '.
  • I 1 ' ⁇ I in ⁇ I 2 ' the following relation exists between a light input intensity I in and a light output intensity I out in the light deflecting element. ##EQU1##
  • the light amplifying element and the light deflecting element were separately explained in the above description. They are connected with each other in series as adjusted in characteristics of the elements to have the following separation ratio of the photo coupler and amplification factor of the amplifier:
  • FIG. 12 shows a combination of the light amplifying element of FIG. 5 with the light deflecting element of FIG. 7 on the above conditions, in which the aperture is an end face of optical fiber.
  • FIG. 13 shows input-output characteristics of the apparatus of FIG. 12.
  • a nonlinear filter may be constructed with a quick rise in I 1 ⁇ I in ⁇ I 2 as enabling light amplification.
  • FIG. 14 shows a construction of a specific apparatus actually arranged in correspondence to the apparatus of FIG. 12.
  • Light traveling straight through a separation photo coupler 52 enters a semiconductor light amplifier 54a to be amplified therein.
  • the thus amplified light is deflected by a semiconductor light deflector 54b.
  • An end of optical fiber is connected to an output end of the semiconductor light deflector 54b as aligned at a suitable angle, whereby components with deflection angle in a predetermined range are extracted from the output light and output from the optical fiber.
  • the other part of light separated by the separation photo coupler 52 is received by a photo detector 54.
  • the light received by the photo detector 54 is converted into an electric signal, and thereafter is amplified by an amplifier 58 to be then input into the semiconductor light amplifier 54a and into the semiconductor light deflector 54b.
  • the following description concerns the examination of light waveform at each of selected portions when an input light waveform is a superposition of sinusoidal wave on direct current light into the apparatus of FIG. 14, based on the fundamentals of operation in the apparatus of FIG. 12.
  • FIG. 15 and FIG. 16 are drawings to show waveforms at selected portions in the apparatus of FIG. 14.
  • Signal (a) is a waveform to show a time change of input light I in .
  • Signal (b) is a waveform to show a time change of input light into the semiconductor light amplifier 54a after separated.
  • the output light may be finally obtained as removing the direct current component, emphasizing the modulation components, and amplifying the peak intensity.
  • the separation ratio of the separation photo coupler 52 may be made variable in this case.
  • the amplification factor of the semiconductor light amplifier 54a may be made variable.
  • the light from the light separating means may be nonlinearly deflected using the saturation characteristics.
  • FIG. 17 shows a light communication system in which a light communication repeater and a light signal pre-amplifier are positioned.
  • a desired light signal is set to have a slightly higher intensity than I 2 , a signal may be obtained in such conditions that only the desired light signal is amplified with uniform intensity because of the saturation of the elements and that optical noises caused for example by scattering are absorbed (that the optical noises are inhibited from being output). (Reference should be made to the waveforms of input and output light in FIG. 2). Then, the repeater has a feature of steep rise in light pulse signal.
  • the signal may be received at a higher S/N ratio in judging on or off at a light receiver. This will be described in more detail below.
  • a receiving side photo detector and a judgement circuit are set to judge on when I out ⁇ 1/2 ⁇ C ⁇ (I 2 2 -I 1 2 ) ⁇ I 2 while off when I out ⁇ 1/2 ⁇ C ⁇ (I 2 2 -I 1 2 ) ⁇ I 2 .
  • I in resulting in I out 1/2 ⁇ C ⁇ (I 2 2 -I 1 2 ) ⁇ I 2 be I x .
  • it is easy to make a range of input light intensity for judging on, ⁇ I
  • FIG. 18 is a drawing to show an embodiment of light intensity change measuring apparatus.
  • the intensity of input light slightly varies as shown.
  • the input light passes through a pulse intensity regenerating apparatus 103 similar to that in FIG. 2, and is then detected by a photo detector 105.
  • An output of the photo detector 105 is detected by a monitor 107 such as an oscilloscope. Then, the waveform of input light with slight intensity change in I x ⁇ I 2 may be observed as enlarged.
  • FIG. 19 is a drawing to show an embodiment of stabilized light source.
  • Light emitted from a variable light source 101 is separated by a light separator 102 into two beams.
  • One of the two separate beams is output to the outside of the system as output light of the stabilized light source.
  • the other beam of the two separate beams is guided through a light pulse intensity regenerating apparatus 103 similar to that in FIG. 2, and is then detected by a photo detector 105.
  • An electric signal output of the photo detector 105 is input into a feedback circuit 109.
  • the feedback circuit 109 compares the intensity of the thus input electric signal with a reference electric signal intensity which is preliminarily set at an intensity of electric signal obtained when the light source 101 emits light with a certain intensity, to detect a difference therebetween, and outputs an electric signal indicating emission of light with an intensity which can compensate the difference.
  • the variable light source 101 changes the intensity of emission light in accordance with a change in value of the electric signal output from the feedback circuit 109.
  • the emission light amount of the light source 101 is thus stabilized, providing a stabilized light source which can provide output light with stable intensity to the outside.
  • the intensity of output light is determined by adjusting the reference electric signal intensity in the feedback circuit 109.
  • the present invention is not limited to the embodiments as described.
  • multiple sets of light pulse intensity regenerating apparatuses as shown in FIG. 2 may be connected in series in order to emphasize the effects thereof.
  • the light pulse intensity regenerating apparatus may be coupled with a saturable absorbing element.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
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US08/051,688 1992-04-24 1993-04-23 Light pulse intensity regenerator, light tranforming repeater, pre-amplifier for light signal, light intensity change measuring apparatus, and stabilized light source Expired - Fee Related US5350913A (en)

Applications Claiming Priority (2)

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JP4-106687 1992-04-24
JP4106687A JPH05303125A (ja) 1992-04-24 1992-04-24 光強度非線形フィルタ、光変換中継器、光信号用プリアンプ及び光強度変化測定器

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5521743A (en) * 1993-12-16 1996-05-28 Rockwell International Corporation Photon-counting spatial light modulator with APD structure
US6580845B1 (en) 2000-08-11 2003-06-17 General Nutronics, Inc. Method and device for switching wavelength division multiplexed optical signals using emitter arrays
WO2004003652A1 (ja) * 2002-06-28 2004-01-08 Fujitsu Limited 反射型可変光偏向器及びそれを用いた光デバイス
WO2005004359A1 (en) * 2003-06-30 2005-01-13 Fujitsu Limited Optical regenerator in optical fiber communication system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4663997B2 (ja) * 2004-03-09 2011-04-06 富士通株式会社 広入力ダイナミックレンジ光増幅器を用いた光伝送装置
JP4754388B2 (ja) * 2006-03-31 2011-08-24 富士通株式会社 光伝送システム

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Publication number Priority date Publication date Assignee Title
US4958231A (en) * 1988-05-13 1990-09-18 Hamamatsu Photonics Kabushiki Kaisha Electro-optical streak camera
US5025142A (en) * 1988-05-26 1991-06-18 Hamamatsu Photonics Kabushiki Kaisha Light waveform changing apparatus using an optical amplifier

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JPS5694679A (en) * 1979-12-27 1981-07-31 Fujitsu Ltd Lightamplifying device
JPS62189830A (ja) * 1986-02-17 1987-08-19 Nec Corp 光中継装置
JP2665231B2 (ja) * 1988-05-13 1997-10-22 浜松ホトニクス株式会社 光波形測定装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4958231A (en) * 1988-05-13 1990-09-18 Hamamatsu Photonics Kabushiki Kaisha Electro-optical streak camera
US5025142A (en) * 1988-05-26 1991-06-18 Hamamatsu Photonics Kabushiki Kaisha Light waveform changing apparatus using an optical amplifier

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5521743A (en) * 1993-12-16 1996-05-28 Rockwell International Corporation Photon-counting spatial light modulator with APD structure
US6580845B1 (en) 2000-08-11 2003-06-17 General Nutronics, Inc. Method and device for switching wavelength division multiplexed optical signals using emitter arrays
WO2004003652A1 (ja) * 2002-06-28 2004-01-08 Fujitsu Limited 反射型可変光偏向器及びそれを用いた光デバイス
US20050068645A1 (en) * 2002-06-28 2005-03-31 Fujitsu Limited Reflective adjustable optical deflector and optical device employing the same
US7280718B2 (en) 2002-06-28 2007-10-09 Fujitsu Limited Reflective adjustable optical deflector and optical device employing the same
WO2005004359A1 (en) * 2003-06-30 2005-01-13 Fujitsu Limited Optical regenerator in optical fiber communication system
US20070104491A1 (en) * 2003-06-30 2007-05-10 Rainer Hainberger Optical regenerator in optical fiber communication system
US7773886B2 (en) 2003-06-30 2010-08-10 Fujitsu Limited Optical regenerator in optical fiber communication system

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DE69332322D1 (de) 2002-10-31
EP0567312B1 (en) 2002-09-25
DE69332322T2 (de) 2003-05-22
JPH05303125A (ja) 1993-11-16
EP0567312A2 (en) 1993-10-27
EP0567312A3 (en) 1994-12-14

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